1. Field of the Invention
The present invention relates to a magnetic code reading device and a magnetic code reading method for a magnetic recording medium such as a bankbook issued by a bank or the like or a credit card, and more particularly, to a device for reading magnetic code on a magnetic recording medium where predetermined information is written in correspondence with a timing pulse generated in correspondence with a moving distance of a magnetic head.
2. Description of Related Art
A bankbook of a bank or the like has a stripe-shaped magnetic recording medium for recording magnetic code, encoding the name of bank branch that issued the bankbook, an account number and the like, attached thereto. Further, in a magnetic card such as a credit card, a similar magnetic recording medium for recording magnetic code relating to a card number and the like is provided.
The bankbook or magnetic card is inserted into a bankbook slot or card slot in an automatic teller machine (hereinafter abbreviated to xe2x80x9cATMxe2x80x9d) or the like, then magnetic code recorded on the magnetic recording medium is read, and predetermined information is recognized.
As a method for recording magnetic code onto a magnetic recording medium, a digital recording method is employed, and various modulation methods are employed for modulating binary data in correspondence with existence/absence of magnetization, direction of magnetization or the like. Typical modulation methods are an NRZI (Non Return to Zero Inverted) method, an FM (Frequency Modulation) method, an MFM (Modified FM) method, (2, 7), (1, 7) coding methods and the like.
Among these modulation methods, the FM method and the coding methods enable self clocking by adding a clock signal to each bit indicative of writing code. In the FM method, for example, in a magnetic head transfer mechanism to move a magnetic head having a magnetic sensor on a surface of the stripe-shaped magnetic recording medium, a timing disk for generating a timing pulse in accordance with a moving distance of the magnetic head is provided, and the timing pulse is used as a clock signal, such that predetermined magnetic code is written onto the magnetic recording medium in synchronization with the rising edge (or falling edge) of the timing pulse.
The magnetic code written in this manner is detected by the magnetic sensor on the magnetic head moving at an almost constant speed on the surface of the magnetic recording medium by the magnetic head transfer mechanism. Then, a serial digital signal relating to the written predetermined information is reproduced based on a series of detected readout magnetic waveforms.
In a magnetic head transfer mechanism as shown in FIG. 1, the timing disk, for generating the above-described timing pulse used in writing magnetic code, has a disk shape to rotate in accordance with rotation of a lead screw to move the magnetic head. The disk C has a plurality of slits at fixed intervals on its periphery. An optical detection sensor, comprising a light emitting device and a photoreception device, is attached to a frame of the magnetic head transfer mechanism such that the devices hold the periphery of the disk therebetween. In this manner, one timing pulse is generated by a unit moving distance of the magnetic head.
However, the ATM or the like is not always installed in a position in an excellent air environment. Further, as the ATM or the like contains a printer for printing the statement of each transaction such as obtaining cash on a rolled paper and cutting the printed paper, paper dust occurs within the cabinet.
The small particles and dust such as paper dust occasionally enter the slits of the timing disk, and prevent the optical detection sensor from precisely detecting the respective slits of the timing disk rotating with the movement of the magnetic head. Accordingly, the above-described timing pulse waveform used in writing magnetic code cannot be generated by the unit moving distance of the magnetic head, and a magnetic waveform written in this state includes a jitter waveform.
In a case where a written magnetic waveform including thus-occurred jitter is read, the waveform representing a binary bit is different from that representing a binary bit indicative of regular xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d, and a xe2x80x9chighxe2x80x9d or xe2x80x9clowxe2x80x9d part extended for the timing clock unit period is detected.
In this case, a magnetic code reading device in a conventional ATM or the like determines that a writing error has occurred and performs uniform error processing. The device determines that the bankbook or magnetic card cannot be recognized and ejects it without performing necessary transaction processing.
By this operation, it is determined that the magnetic data must be written onto the bankbook or magnetic card again, and the bankbook or magnetic card cannot be used for such operation. Also, it is determined that correction must be performed on the ATM or the like, and it cannot be used.
The present invention has been made in view of the fact that even though a readout magnetic waveform includes jitter, there is no problem in magnetic code reading and recognition processing in a predetermined case, and provides a magnetic code reading device comprising a magnetic head having a magnetic sensor for writing and reading magnetic code onto/from a magnetic recording medium, a timing disk for generating a timing pulse in correspondence with a moving distance of said magnetic head, and a controller for controlling said magnetic head and said timing pulse, wherein upon reading of magnetic code on the magnetic recording medium where predetermined information is written in correspondence with said timing pulse, if jitter appears at fixed intervals, corresponding to a rotational period of said timing disk, in a series of readout magnetic waveforms detected by said magnetic sensor, said controller recognizes said magnetic code based on said series of readout magnetic waveforms including the jitter, while if jitter not related to the rotational period of said timing disk appears, said controller performs reading error processing.
The controller has a storage buffer for temporarily storing a serial digital signal detected based on said series of readout magnetic waveforms detected by said magnetic sensor, and the controller detects the existence or absence of jitter repeated at relatively fixed intervals corresponding to the rotational period of said timing disk, in the serial digital signal.
Further, the present invention provides a method for reading magnetic code on a magnetic recording medium where predetermined information is written in correspondence with a timing pulse generated by a unit moving distance of a magnetic head having a magnetic sensor, comprising: a step of outputting a serial digital signal based on a series of readout magnetic waveforms detected by said magnetic sensor; a step of temporarily storing said serial digital signal into a storage buffer; a step of detecting existence or absence of jitter repeated at fixed intervals corresponding to a rotational period of a timing disk for generating said timing pulse, in said serial digital signal; and a step of, if said jitter appears repeated at relatively fixed intervals, correcting said jitter based on said serial digital signal including said jitter and recognizing said magnetic code, while if jitter appears asynchronous to the rotational period of said timing disk, performing reading error processing.